The present invention is directed to a cable which can be used either as an electrical cable or optical cable and has a cladding that comprises imprints produced from a plastic powder.
British Patent No. 1,257,769, which claims priority from German Application 19 51 597, discloses a cable which has imprints on a cable cladding or sheath. The raised imprints are formed by sintering a plastic powder on the cable cladding, and this powder should be selected as close as possible to or the same material as the cable cladding. White or chromatically pigmented low-density polyethylene (LDPE) powders are usually used for the black LDPE claddings, which are resistant to stress tears and are usually employed as a cladding. For example, plastic powders that are known under the tradenames xe2x80x9cPECMA 200xe2x80x9d or xe2x80x9cCEVAMxe2x80x9d, which is an acrylic acid copolymer sold by Interorgana of Stuttgart, Germany, are used as products for the imprinting.
In addition to having a good workability and adequate adhesion, the plastic powders used for the imprinting must be of such a nature that they do not lead to any stress cracks. Mechanically, the imprinting of the respective identifier to be applied on the cable cladding or sheath represent a certain intervention that intrinsically harbors the risk of forming stress cracks.
The present invention is based on the object of creating a plastic powder suitable for the imprinting, wherein the protection of the cable cladding against the formation of stress cracks is also assured to the farthest-reaching extent possible in addition to providing a good workability.
To accomplish these objects, the invention is directed to an improvement in a cable having a core with a cable cladding that comprises imprints manufactured of a plastic powder. The improvement is achieved in that the plastic powder contains copolymers of ethylene with unpolar comonomers.
The plastic powder, which is constituted according to the present invention, can be easily worked, yields good adhesion and, as investigations have shown, harbors far less of a risk of forming stress cracks.
Suitable copolymers of ethylene with unpolar comonomers for the inventive plastic powder are preferably commercially available as linear low density polyethylene (LLDPE) as well as very low density polyethylene (VLDPE). For example, powders offered under the tradenames xe2x80x9cATTANAxe2x80x9d and xe2x80x9cENGAGE POPxe2x80x9d as well as xe2x80x9cENGAGE POExe2x80x9d of Dow Chemical as well as xe2x80x9cCLEARFLEXxe2x80x9d of ENI-Chemie are particularly suitable. Altogether good results with respect to the resistance to stress cracks were capable of being achieved in tests with the aforementioned materials.
Linear polyethylenes that, in particular, contain alpha olefins, preferably alpha-olefin propene, butene, hexene, octene and mixtures thereof as comonomers are preferably employed.
The proportion of comonomers within the plastic powder should be advantageously selected so that the reduced density of the ethylene copolymer caused by the comonomers is less than or equal to 0.92.
Various additives can also be added to the plastic powder within the scope of the invention, especially those for optimizing the adhesion, such as, for example, ethylene copolymers with polar comonomers, such as ethylene vinyl acetate (EVA) copolymers.
Additional stabilizers against heat and/or light as well as potentially anti-oxidants can also be advantageously added to the plastic powder of the invention. Including chromatic pigments into the plastic powder for improving the visibility or the legibility of the imprint is also expedient.
The plastic powder of the invention should expediently have a grain fineness with a grain diameter in a range of 50 xcexcm through 200 xcexcm.
Other advantages and features of the invention will be readily apparent from the following description of the preferred embodiments, the drawing and claims.